Every so often, the GDG number for input log datasets rolls over from 9999 to 0001.
This causes PCFREG to STOP REGISTERING datasets. In consequence, nothing gets collected.
To fix this, run PCFDEL99 after PCFREG until there are no longer any 9nnn generations in the catalog.
This situation arises only once every 5-7 years (at current rate); it is next expected about 2010. Enjoy (or retire first).